#!/usr/bin/env python3
"""Kookabus-01 reader for Linux Python (Raspberry Pi, Jetson...).

    pip install smbus2 && python3 kookabus.py [bus] [addr]
"""
import sys
import time

R_SHUNT = 0.005       # ohm; trim against a multimeter if current reads off
I_LSB = 0.0005        # A per CURRENT bit
CAL = round(0.00512 / (I_LSB * R_SHUNT))  # 2048
CONFIG = 0x4527       # 16-sample average, 1.1 ms conversions, continuous

CELLS = 5
R_PATH = 0.03 + 0.10  # ohm: board + an assumed pack resistance, for sag correction
V_CUTOFF = 3.0 * CELLS

# Resting Li-ion cell voltage -> % (typical NMC; tune for your packs)
OCV = ((3.00, 0), (3.30, 5), (3.45, 10), (3.60, 20), (3.70, 35),
       (3.80, 50), (3.90, 65), (4.00, 78), (4.10, 90), (4.20, 100))


def soc(pack_v, cells=CELLS):
    v = pack_v / cells
    if v <= OCV[0][0]:
        return 0
    for (v0, p0), (v1, p1) in zip(OCV, OCV[1:]):
        if v <= v1:
            return p0 + (p1 - p0) * (v - v0) / (v1 - v0)
    return 100


class Kookabus:
    def __init__(self, bus=1, addr=0x40):
        from smbus2 import SMBus
        self.bus, self.addr = SMBus(bus), addr
        if self._r(0xFE) != 0x5449:
            raise OSError(f"no INA226 at 0x{addr:02x}")
        self._w(0x00, CONFIG)
        self._w(0x05, CAL)

    # The INA226 is big-endian; SMBus word transfers are little-endian.
    def _w(self, reg, val):
        self.bus.write_i2c_block_data(self.addr, reg, [val >> 8, val & 0xFF])

    def _r(self, reg):
        hi, lo = self.bus.read_i2c_block_data(self.addr, reg, 2)
        return hi << 8 | lo

    def voltage(self):
        return self._r(0x02) * 0.00125

    def current(self):
        raw = self._r(0x04)
        return (raw - 0x10000 if raw & 0x8000 else raw) * I_LSB

    def power(self):
        return self._r(0x03) * 25 * I_LSB


if __name__ == "__main__":
    kb = Kookabus(int(sys.argv[1]) if len(sys.argv) > 1 else 1,
                  int(sys.argv[2], 0) if len(sys.argv) > 2 else 0x40)
    while True:
        v, i, p = kb.voltage(), kb.current(), kb.power()
        low = "  LOW - stop the load" if v < V_CUTOFF else ""
        print(f"{v:6.2f} V  {i:6.3f} A  {p:6.1f} W  ~{soc(v + i * R_PATH):3.0f} %{low}", flush=True)
        time.sleep(1)